This invention relates generally to positioning and feeding systems for use within sawmills. More particularly, it relates to a positioning and feed system for use in secondary breakdown machines such as edgers and rotary gangs.
In almost all typical modern sawmills, individual logs are first broken down longitudinally at a primary breakdown station. This step normally produces at least one cant having two flat surfaces and usually two curvilinear surfaces representing portions of the log surface. In addition, side boards are usually produced, also having two flat surfaces and two curvilinear surfaces. Slabs are also produced having one flat surface with the balance being a portion of the log surface. These resulting pieces then undergo further breakdown at secondary breakdown stations. Boards-that is, relatively thin pieces that are suitable for being edged into a dimensional product-will be directed to edging machines while the larger, thicker, wider cants will be directed to rotary gang machines for further breakdown into a plurality of rectangular pieces of dimension lumber with some resulting edgings.
When cants and unedged boards are cut from a log that has bow or curvature in it, the resulting piece will also have a curved axis in the longitudinal direction. It has been recognized that in order to gain the optimum number of pieces or value from a cant or board that has curvature in it, skewing and offset with respect to the center line is necessary. By being able to skew a cant or board to account for bow, knots, wane and other defects affecting the angle of cut, it has been determined that approximately five percent additional lumber recovery may be obtained. Once the cant or board is optimally positioned by skewing and offsetting with reference to the saw lines, it must then be transported through the saws in the same orientation.
In the past, most sawing machines have utilized so-called "line bars" which simply adjust the lateral position or offset of a cant or board before it is transported into the saws. Line bar mechanisms do not allow for skewing and, therefore, cannot provide optimum positioning for maximum lumber recovery.
Other systems to provide better positioning utilize retractable, skewable stops or pins in place of a line bar to position cants or boards ahead of a sawing machine. Whenever a workpiece is individually positioned after having been conveyed transversely from one direction to then be fed in a longitudinal direction, time is wasted while the workpiece is being positioned. It, thus, would be desirable to not only provide the optimum positioning capability but also a system that maintains the overall production through the positioning and feed system.
Thus, from the foregoing, one object of the present invention is to optimally position a cant or board with respect to the saws prior to being fed into the sawing machine.
A further object of this invention is to increase the number of cants or boards that are fed through the sawing machine in the more optimum orientation.
These, and many other objects of the present invention, will be better understood and more fully appreciated upon reading the specification to follow in conjunction with the attached drawings.